Polybenzimidazole solution in an ionic liquid

ABSTRACT

A polybenzimidazole solution comprises a polybenzimidazole dissolved in an ionic liquid excluding 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium hydroxide, and 1-butyl-3-methylimidazolium tetrafluoroborate.

RELATED APPLICATIONS

The instant application claims the benefit of co-pending ProvisionalApplication Ser. No. 61/288,479 filed Dec. 21, 2009.

FIELD OF THE INVENTION

The instant invention is directed to a solution where polybenzimidazolepolymer is dissolved in an ionic liquid.

BACKGROUND OF THE INVENTION

Polybenzimidazoles (PBI), particularly aromatic PBIs, are characterizedby a high degree of thermal stability and a great resistance todegradation by heat and hydrolytic and oxidizing media.

PBIs are not easy to make and once made, they are difficult to process.PBIs are made by a melt condensation reaction where monomers arepolymerized, at high temperatures, to form a friable foam, the foam iscrushed, and optionally the crushed PBI is further polymerized in asolid state. Since it is highly heat stable, the PBI resin must bedissolved, in the organic solvents mentioned below, for subsequent use,such as coatings and shaped articles (e.g., fibers, films, membranes,sheets, rods, billets, slabs).

PBIs are most commonly dissolved, by heating, in highly polar, aproticorganic solvents. Those solvents include: N, N-dimethylacetamide (DMAc);N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), andN-methyl-2-pyrrolidone (NMP). While these solvents are effective, theyare most often considered environmentaly unfriendly. See generally,Wang, B., et al., Dissolution and regeneration of polybenzimidazolesusing ionic liquids, European Polymer Journal, EPJ 45 (2009) pages2962-2965.

Recently, it has been reported that PBIs may be dissolved in certainionic liquids. Wang, et al., Ibid. PBI is reported to have dissolved in1-butyl-3-methylimidazolium chloride ([BMIM]Cl),1-butyl-3-methylimidazolium hydroxide ([BMIM]OH), and1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄).

Accordingly, there is a need for new solvents for PBI. Such solventscould replace the typically used organic solvents for the preparation ofPBI solutions.

SUMMARY OF THE INVENTION

A polybenzimidazole solution comprises a polybenzimidazole dissolved inan ionic liquid excluding 1-butyl-3-methylimidazolium chloride,1-butyl-3-methylimidazolium hydroxide, and 1-butyl-3-methylimidazoliumtetrafluoroborate.

DESCRIPTION OF THE INVENTION

Polybenzimidazole (PBI) refers to, for example, the product of the meltpolymerization of an tetraamine (e.g., aromatic and heteroaromatictetra-amino compounds) and a second monomer being selected from thegroup consisting of free dicarboxylic acids, alkyl and/or aromaticesters of dicarboxylic acids, alkyl and/or aromatic esters of aromaticor heterocyclic dicarboxylic acid, and/or alkyl and/or aromaticanhydrides of aromatic or heterocyclic dicarboxylic acid. Furtherdetails may be obtained from U.S. Pat. Nos. Re 26065; 4,506,068;4,814,530; and US Publication No. 2007/0151926, each of which isincorporated herein by reference. The PBI polymer may have an IV(inherent viscosity), discussed in detail in the experimental sectionbelow, in the range of 0.10-2.00 dL/g.

The aromatic and heteroaromatic tetra-amino compounds, used inaccordance with the invention, are preferably3,3′,4,4′-tetra-aminobiphenyl, 2,3,5,6-tetra-aminopyridine,1,2,4,5-tetra-aminobenzene, 3,3′,4,4′-tetra-aminodiphenylsulfone,3,3′,4,4′-tetra-aminodiphenyl ether, 3,3′,4,4′-tetra-aminobenzophenone,3,3′,4,4′-tetra-aminodiphenyl methane, and3,3′,4,4′-tetra-aminodiphenyldimethylmethane, and their salts, inparticular, their mono-, di-, tri-, and tetrahydrochloride derivatives.

The aromatic carboxylic acids used, in accordance with the invention,are dicarboxylic acids or its esters, or its anhydrides or its acidchlorides. The term “aromatic carboxylic acids” equally comprisesheteroaromatic carboxylic acids as well. Preferably, the aromaticdicarboxylic acids are isophthalic acid, terephthalic acid, phthalicacid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid,2-hydroxyterephthalic acid, 5-aminoisophthalic acid,5-N,N-dimethylaminoisophthalic acid, 5-N,N-diethylaminoisophthalic acid,2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid,4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid,2,4-dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 3-fluorophthalicacid, 5-fluoroisophthalic acid, 2-fluoroterephthalic acid,tetrafluorophthalic acid, tetrafluoroisophthalic acid,tetrafluoroterephthalic acid, 1,4-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,2,7-napthalenedicarboxylic acid, diphenic acid,1,8-dihydroxynaphthalene-3,6-dicarboyxlic acid, diphenylether-4,4′-dicarboxylic acid, benzophenone-4,4′-dicarboxylic acid,diphenylsulfone-4,4′-dicarboyxlic acid, biphenyl-4,4′-dicarboxylic acid,4-trifluoromethylphthalic acid,2,2-bis(4-carboxyphenyl)hexafluoropropane, 4,4′-stilbenedicarboxylicacid, 4-carboxycinnamic acid, or their C1-C20-alkyl esters orC5-C12-aryl esters, or their acid anhydrides or their acid chlorides.

The heteroaromatic carboxylic acids used, in accordance with theinvention, are heteroaromatic dicarboxylic acids or their esters ortheir anhydrides. The “heteroaromatic dicarboxylic acids” includearomatic systems that contain at least one nitrogen, oxygen, sulfur, orphosphorus atom in the ring. Preferably, it is pyridine-2,5-dicarboxylicacid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid,pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridine dicarboxylic acid,3,5-pyrazole dicarboxylic acid, 2,6-pyrimidine dicarboxylic acid,2,5-pyrazine dicarboxylic acid, 2,4,6-pyridine tricarboxylic acid, andbenzimidazole-5,6-dicarboxylic acid, as well as their C1-C20-alkylesters or C5-C12-aryl esters, or their acid anhydrides or their acidchlorides.

The aromatic and heteroaromatic diaminocarboxylic acid used inaccordance with the invention is preferably diaminobenzoic acid and itsmono- and dihydrochloride derivatives.

Preferably, mixtures of at least 2 different aromatic carboxylic acidsare used. These mixtures are, in particular, mixtures ofN-heteroaromatic dicarboxylic acids and aromatic dicarboxylic acids ortheir esters. Non-limiting examples are isophthalic acid, terephthalicacid, phthalic acid, 2,5-dihydroxyterephthalic acid,2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid,2,3-dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid,3,4-dihydroxyphthalic acid, 1,4-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,2,7-naphthalenedicarboxylic acid, diphenic acid,1,8-dihydroxynapthalene-3,6-dicarboxylic acid, diphenylether-4,4′-dicarboxylic acid, benzophenone-4,4′-dicarboxylic acid,diphenylsulfone-4,4′-dicarboxylic acid, biphenyl-4,4′-dicarboxylic acid,4-trifluoromethylphthalic acid, pyridine-2,5-dicarboxylic acid,pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid,pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid,3,5-pyrazoledicarboxylic acid, 2,6-pyrimidine dicarboxylic acid, and2,5-pyrazine dicarboxylic acid. Preferably, it is the diphenylisophthalate (DPIP) and its ester.

Examples of polybenzimidazoles which may be prepared according to theprocess as described above include:

-   poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole;-   poly-2,2′-(biphenylene-2″2″)-5,5′-bibenzimidazole;-   poly-2,2′-(biphenylene-4″4″)-5,5′-bibenzimidazole;-   poly-2,2′-(1″,1″,3″trimethylindanylene)-3″5″-p-phenylene-5,5′-bibenzimidazole;-   2,2′-(m-phenylene)-5,5′-bibenzimidazole/2,2-(1″,1″,3″-trimethylindanylene)-5″,3″-(p-phenylene)-5,5′-bibenzimidazole    copolymer;-   2,2′-(m-phenylene)-5,5-bibenzimidazole-2,2′-biphenylene-2″,2″′-5,5′-bibenzimidazole    copolymer;-   poly-2,2′-(furylene-2″,5″)-5,5′-bibenzimidazole;-   poly-2,2′-(naphthalene-1″,6″)-5,5′-bibenzimidazole;-   poly-2,2′-(naphthalene-2″,6″)-5,5′-bibenzimidazole;-   poly-2,2′-amylene-5,5′-bibenzimidazole;-   poly-2,2′-octamethylene-5,5′-bibenzimidazole;-   poly-2,2′-(m-phenylene)-diimidazobenzene;-   poly-2,2′-cyclohexenyl-5,5′-bibenzimidazole;-   poly-2,2′-(m-phenylene)-5,5′-di(benzimidazole)ether;-   poly-2,2′-(m-phenylene)-5,5′-di(benzimidazole)sulfide;-   poly-2,2′-(m-phenylene)-5,5′-di(benzimidazole)sulfone;-   poly-2,2′-(m-phenylene)-5,5′-di(benzimidazole)methane;-   poly-2,2″-(m-phenylene)-5,5″-di(benzimidazole)propane-2,2; and-   poly-ethylene-1,2-2,2″-(m-phenylene)-5,5″-dibenzimidazole)ethylene-1,2-   where the double bonds of the ethylene groups are intact in the    final polymer. Poly-1,2′-(m-phenylene)-5,5′-bibenzimidazole, a    preferred polymer, can be prepared by the reaction of    3,3′,4,4′-tetraaminobiphenyl with a combination of isophthalic acid    with diphenyl isophthalate or with a dialkyl isophthalate such as    dimethyl isophthalate; a combination of diphenyl isophthalate and a    dialkyl isophthalate such as dimethyl isophthalate; or at least one    dialkyl isophthalate such as dimethyl isophthalate, as the sole    dicarboxylic component.

Ionic liquids, which have previously been known as liquid electrolytes,ionic melts, ionic fluids, fused salts, liquid salts, and ionic glasses,refer to salts that form stable liquids. More specfically, ionic liquidsrefer to salts that have a melting temperature below 100° C., or, thatare liquid at room temperature. Further information about ionic liquidsmay be obtained from: Ionic Liquid, Wikipedia(en.wikipedia.org/wiki/Ionic_liquid), 2009; and Abbott, A., & Davies,D., “Salty Solvents—Ionic really,” Royal Society of Chemistry(www.rsc.org/Education/EiC/issues/2005 _Jan/salty.asp), January, 2005;Winterton, N., Solubilization of Polymers by ionic liquids, J. Mater.Chem., 2006, 16, pages 4281-4293, each of which is incorporated hereinby reference.

Generally, such ionic liquids consist of a cation (+) and an anion (−).The cations may include, but is not limited to, choline, ammoniums(e.g., quaternary ammoniums), phosphoniums, pyridiniums, pyrrolidiniums,morpholiniums, pyrazoliums, sulfoniums, and imidazoliums. The anions mayinclude, but are not limited to, halides, bis (triflyl) amide [akatriflamide, bistriflimide, (CF₃SO₂)₂N⁻], CF₃SO₃ ⁻ [akatrifluoromethanesulfonate or triflate], nitrates, sulfates, acetates,cyanates, aluminates, borates (e.g., BF₄ ⁻), phosphates (e.g., PF₆ ⁻),phosphorates (e.g., PO₃ ⁻), hydroxides, alkylsulfates (e.g., methanesulfate, ethylene sulfate), tosylate.

Such ionic liquids may specifically include: choline chloride/ureamixtures, choline chloride/oxalic acid mixtures,1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazoliumchloride, 1-ethyl-3-methylimidazolium bis (triflyl) amide,1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methylimidazoliumdiethyl sulfate, 1-ethyl-3-methylimidazolium formate,1-ethyl-3-methylimidazolium bis(trifluoromethane) sulfonamide,1-ethyl-3-methylimidazolium phosphate, 1-methylimidazolium hydrogensulfate, 1-butyl-1-methylpyrrolidinium trifluoromethylsulfate,1-allyl-3-methylimidazolium acetate, 1-allyl-3-methylimidazoliumchloride, 1-butyl-3-methylimidazolium acetate,1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazoliumdicyanoamide, 1-butyl-3-methylimidazolium formate,1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazoliumhydroxide, 1-butyl-3-methylimidazolium hydrogen sulfate, N-methylmorpholine N oxide (i.e., the solvent used for Tencel/Lyocel),1-hexyl-3-methylimidazolium chloride, 1-butyl-2,3-dimethylimidazoliumchloride, 1-allyl-2,3-diemthylimidazolium bromide,1-butyl-3-methylpyridinium chloride, N-ethylpyridinium chloride,benzyldimethyl (tetradecyl)-ammonium chloride, 1,3-dibutylimidazoliumbromide, 1,3-dibutylimidazolium tetrafluoroborate. Additional ionicliquids may be gleaned from: Wang, B, et al., Dissolution andregeneration of polybenzimidazoles using ionic liquids, European PolymerJournal 45 (2009) 2962-2965, Ionic Liquid, Wikipedia(en.wikipedia.org/wiki/Ionic_liquid), 2009; and Abbott, A., & Davies,D., “Salty Solvents—Ionic really,” Royal Society of Chemistry(www.rsc.org/Education/EiC/issues/2005 _Jan/salty.asp), January, 2005;Winterton, N., Solubilization of Polymers by ionic liquids, J. Mater.Chem., 2006, 16, pages 4281-4293, Vitz, J., et al., Extended dissolutionstudies of cellulose in imidazolium based ionic liquids, Green Chem.,2009, 11, 417-424; Liebert, T, et al., Interaction of ionic liquids withpolysaccharides, Bioresources (2008) 3(2), 576-601; Vygodski, Y. S.,Synthesis of polymers in ionic liquids as new reaction media, DokladyChemistry (2001) vol. 381, nos 4-6, pp 353-355;www.basionics.com/en/ionic-liquids Frequently asked questions, each ofwhich is incorporated herein by reference. In one embodiment,1-ethyl-3-methylimidazolium acetate (EMIM acetate),1-butyl-3-methylimidazolium acetate (BMIM acetate), and mixtures thereofare preferred.

PBI solutions in ionic liquids may be made by mixing the PBI polymerinto the ionic liquid (or a mixture of ionic liquids). In oneembodiment, this mixing is with agitation (e.g., stirring). In anotherembodiment, the mixing is with agitation and heat (heat including anyexternal energy source, such as, for example, thermal and/or radiant(e.g., infrared (IR) and/or microwave)). In yet another embodiment, themixing is with agitation, heat, and in an inert atmosphere (e.g., anitrogen (N₂) purge or blanket). In one embodiment, when heat is used,the temperature should not exceed the temperature of decomposition ofthe ionic liquid. The time for dissolution may be any time. In oneembodiment, the dissolution time may be less than 48 hours. In anotherembodiment, the dissolution time may be less than 24 hours. In yetanother embodiment, the dissolution time may be less than 12 hours.

PBI solutions may have any % solid. In one embodiment, the % solidsrange from 0.1-99.0% solids. In another embodiment, the % solids mayrange from 0.1-90.0%. In another embodiment, the % solids may range from20.0-70.0%. In yet another embodiment, the % solids may range from30.0-60.0%. In other embodiments, the % solids are up to 35.0% (e.g.,0.1-35.0%) and most practically, based on experimental work disclosedherein in the range of 10.0-15.0%.

PBI polymer may be recovered (regenerated) from the PBI solutions byadding the PBI solution into a bath of material capable of precipitatingor coaguluating the dissolved PBI polymer. Such materials include, butare not limited to, water, alcohols (e.g., methanol), and mixturesthereof. The PBI solution may be slowly added to the precipitating(coagulating) bath and the dissolved PBI polymer falls out of thesolution. Thereafter, the precipitated polymer is harvested, and washedand dried, as necessary, for subsequent processing. Washing may beaccomplished by the precipitating material. Drying is preferrablyaccomplished in an inert atmosphere.

PBI solutions in ionic liquids may be used to form dopes for coating oradhesive applications; or used in the wet spinning of PSI filaments; orwet forming of films, membranes (porous and non-porous), rod, billets,or slabs; or in mixing/blending (fabrication) of PBIs with otherpolymers (e.g., PEEK, PEK, etc.) or materials or additives.

The foregoing is further illustrated with reference to the followingnon-limiting examples of the instant invention.

Examples

Dissolution of the polybenzimidazole in the ionic liquid was performedby adding a known quantity of PBI polymer to a 250 ml, three-neck, roundbottom flask equipped with a water-cooled condenser, thermometer, andnitrogen purge; or a round bottom flask in a heating mantle/voltageregulator with a condenser and thermometer; or a beaker/Erlenmeyer flaskon a hot plate with a magnetic stirrer. A weighed amount of ionic liquidwas added to the flask. PBI polymer, prior to use, was dried in a vacuumoven at 150-180° C. with a nitrogen purge for at least one hour. Aweighed amount of the dried PBI was added to the flask. The contents ofthe flask, weighed ionic liquid and PBI polymer, was stirred and purgedwith nitrogen, and the temperature was monitored. The contents of theflask were heated so as not to exceed the decomposition temperature ofthe ionic liquid, typically 150-200° C., with and without stirring. Theweight of the PBI polymer was increased to determine the maximum solidslevel achievable under the conditions used. A collector flask wasattached to the condensor in order to collect any condensates orby-products.

Regeneration of the PBI polymer from solution was performed by slowingadding the solution to stirred water. The PBI polymer wasprecipitated/coagulated from the solution. The recovered PBI polymer waswashed with copius amounts of water, filtered, and then dried. Therecovered PBI polymer was characterized for IV (inherent viscosity) andby molecular spectroscopy.

The results of the solutioning and regeneration of various PBI polymersin various ionic liquids are reported in Table 1 and discussed below.

Based upon the analysis of the regenerated PBI polymer and the collectedcondensates, only dissolution of the PBI polymer in the ionic liquidoccurred. The regenerated PBI polymer closely resembled the starting PBIpolymer with some residual ionic liquid, and the condensates showedmainly the ionic liquid decomposition products with some impurities.

The regenerated PBI polymer was found to have better dissolutioncharacteristics compared to the starting materials. Presumably, this wasdue to the elimination of cross-linked high IV polymer and gels. IV's ofthe regenerated PBI polymers were found to decrease slightly upondissolution and precipitation from the starting materials; presumablydue to morphology changes and the elimination of high IV gel fractions.

TABLE 1 % PBI Temp.³ IV⁴ (dL/g) Solvent Solids¹ polymer² (° C.) HoldTime before/after Stability⁵ Control⁶ 9.00 0.8 — — 0.80/0.74 — EMIM⁷acetate 9.08 0.8 185 — 0.89/0.70 4+ months 23.10 0.8 187 — 0.89/0.64 4+months 34.80 0.8 180 — — 3+ months 13.90 0.5 185 — 0.41/0.66 4+ months5.02 0.2 155-171 1 hr 0.20/0.13 — 8.58 0.2 390 — 0.20/0.21 — 9.39 0.2392 — 0.25/0.26 — 10.20 0.2 360 — 0.22/0.24 — BMIM⁸ acetate 8.65 0.8 190— 0.89/0.83 4+ months 17.00 0.8 180 — 0.89/0.80 4+ months 8.87 0.2 20033 min — — 9.34 0.2 300-325 2 hr 20 min 0.20/0.20 — 19.50 0.2 192 42 min— — Choline chloride + urea 15.00 0.2 200-246 40 min — — Cholinechloride + oxalic acid 4.99 0.2 140-149 1.25 hr 0.20/0.17 — 9.19 0.2147-169 3.5 hr 0.20/0.17 — EMIM diethyl phosphate 15.02 0.2 123 2 hr — ND⁹ 15.02 0.2 150 1 hr — ND 15.02 0.2 192 45 min — ND ¹% solids ={solute (g)/[solute (g) + solvent (g)]} × 100 ²PBI polymer is identifiedby IV, inherent viscosity (dL/g), discussed in detail below. ³Temp. isthe maximum temperature during dissolution of the polymer ⁴IV (inherentvisosity), as used herein, is the ratio of the specific viscosity of asolution of known concentration to the concentration of the soluteextrapolated to zero concentration, measured in units of dL/g(deciliters/gram). It is directly proportional to the polymer-averagemolecular weight, and is based on the concentration of the polymersample tested, g/100 ml or g/deciliter. The polymer is dissolved at the0.4% (w/v) level in 100 ml of 96.5% (+/−0.5%) sulfuric acid at 80 C.After filtering, an aliquot is measured for IV using a calibratedCannon-Fenske capillary viscometer in a 25 C. (+/−0.1 C.) water bath,the flow time (sec.) of the PBI polymer solution measured vs. thedissolving solvent: IV = ln (t₁/t₂)/c, where the natural log of the flowtime of the PBI solution (t₁) over the flow time of the solvent (t₂) isdivided by the PBI solution concentration (c). ⁵Stability repesents thetime observed and not necessarily the maximum time of stability. ⁶PBI inDMAc ⁷EMIM = 1-ethyl-3-methylimidazolium ⁸BMIM =1-butyl-3-methylimidazolium ⁹ND indicates that the polymer did notdissolve.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicated the scope of the invention.

1. A polybenzimidazole solution comprising: a polybenzimidazoledissolved in an ionic liquid excluding 1-butyl-3-methylimidazoliumchloride, 1-butyl-3-methylimidazolium hydroxide, and1-butyl-3-methylimidazolium tetrafluoroborate.
 2. The polybenzimidazolesolution according to claim 1 wherein said ionic liquid being a salthaving a melting point less than or equal to 100° C.
 3. Thepolybenzimidazole solution according to claim 2 where said salt having acation (+) and an anion (−), said cation being selected from the groupconsisting of: choline, ammoniums, phosphoniums, pyridiniums,pyrrolidiniums, morpholimiums, pyrazoliums, sulfoniums, imidazoliums,and said anion being selected from the group consisting of: halides, bis(triflyl) amide, CF₃SO₃ ⁻, hydroxides, nitrates, sulfates, acetates,cyanates, aluminates, borates, phosphates, phosphorates, alkylsulfates,tosylates.
 4. The polybenzimidazole solution according to claim 1wherein said ionic liquid being selected from the group consisting of:choline chloride/urea mixtures, choline chloride/oxalic acid mixtures,1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazoliumchloride, 1-ethyl-3-methylimidazolium bis (triflyl) amide,1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methylimidazoliumdiethyl sulfate, 1-ethyl-3-methylimidazolium formate,1-ethyl-3-methylimidazolium bis(trifluoromethane) sulfonamide,1-ethyl-3-methylimidazolium phosphate, 1-methylimidazolium hydrogensulfate, 1-butyl-1-methylpyrrolidinium trifluoromethylsulfate,1-allyl-3-methylimidazolium acetate, 1-allyl-3-methylimidazoliumchloride, 1-butyl-3-methylimidazolium acetate,1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazoliumdicyanoamide, 1-butyl-3-methylimidazolium formate,1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazoliumhydroxide, 1-butyl-3-methylimidazolium hydrogen sulfate, N-methylmorpholine N oxide (i.e., the solvent used for Tencel/Lyocel),1-hexyl-3-methylimidazolium chloride, 1-butyl-2,3-dimethylimidazoliumchloride, 1-allyl-2,3-diemthylimidazolium bromide,1-butyl-3-methylpyridinium chloride, N-ethylpyridinium chloride,benzyldimethyl (tetradecyl)-ammonium chloride, 1,3-dibutylimidazoliumbromide, 1,3-dibutylimidazolium tetrafluoroborate, and mixtures thereof.5. The polybenzimidazole solution according to claim 1 wherein saidionic liquid being selected from the group consisting of:1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazoliumacetate, and mixtures thereof.
 6. The polybenzimidazole solutionaccording to claim 1 having a % solids up to 35.0%.
 7. Thepolybenzimidazole solution according to claim 1 wherein said ionicliquid excludes 1-ethyl-3-methylimidazolium diethyl phosphate.